1. Technical Field
The present invention relates to a self-aligned optical subassembly and, more particularly, to a method of processing a silicon substrate to form a self-aligned optical subassembly.
2. Description of the Prior Art
An important factor in the design and implementation of optical communication systems is the cost and complexity of the packaging for the optical subsystem (i.e., the active optical device, coupled optical fiber and, perhaps, associated electronics). In recent years, advances in packaging have progressed from machined metal piece parts to combinations of metal components and silicon-based components. Advantageously, silicon processing is well-known, relatively inexpensive, and provides for the ability to form a package structure including optically aligned features.
An exemplary utilization of silicon in the formation of a subassembly for optoelectronic devices is disclosed in U.S. Pat. No. 4,945,400 (Blonder et at.) issued Jul. 31, 1990 and assigned to the assignee of record in this application. In general, Blonder et al. disclose a subassembly including a semiconductor (e.g., silicon) base and lid including a variety of etched features (e.g., grooves, cavities, alignment detents) and metallization patterns (e.g., contacts, reflectors) which enable the optoelectronic device to be reliably and inexpensively mounted on the base and coupled to a communicating optical fiber. In particular, Blonder et al. disclose an arrangement wherein the optoelectronic device (e.g., LED) is disposed within a cavity formed by a lid member and the communicating fiber is positioned along a groove formed in a base member. A reflective metallization is utilized to optically couple the device to the fiber. Therefore, positioning of the device over the reflector is the only active alignment step required to provide coupling. Any remaining alignments are accomplished utilizing fiducial features formed in the base and lid members.
Although the Blonder et al. subassembly represents a significant advance in the filed of silicon optical bench packaging, a need remains for providing an arrangement which requires no active alignments to be performed. The provision of a completely passive optical packaging ,arrangement being considered both more reliable and less expensive than virtually any alternative requiring active alignment between components.